Retroreflective sheeting is sometimes adhered to painted surfaces, polymeric articles, or other substrates from which gaseous vapors evolve after the sheeting has been adhered in place. Such vapor evolution has caused blistering of prior-art reflective sheeting, especially when the vapor has evolved rapidly or in large volumes, leaving the sheeting with an unsightly appearance and creating a source of delamination, tearing, or other failure of the sheeting.
Prior-art retroreflective sheeting is rather thick and comprises several layers, and all of these layers undoubtedly contribute to inhibiting migration of vapors. However, our experiments reveal that a metallic specularly reflective layer included in the sheeting is a primary cause of the blistering. Sheeting made without the metallic layer allows sufficient migration of vapors to avoid the previously experienced blistering.
However, retroreflective sheeting made without a metallic specularly reflective layer underlying the transparent microspheres also provides a very low level of retroreflection. A specularly reflective layer is essential, and the blistering problem must be avoided while still retaining such a layer. Insofar as known, no one has previously taught how to do that.